A light-year is not a measure of time, but rather a measure of distance. It's the distance that light travels in one year. Here's how it's calculated:

* Speed of Light: Light travels at an incredibly fast speed, approximately 299,792,458 meters per second (or about 186,282 miles per second).

* Time: A year is defined as 365.25 days, which translates to 31,557,600 seconds.

* Calculation: Multiply the speed of light by the number of seconds in a year to get the distance light travels in one year:

299,792,458 m/s * 31,557,600 s = 9,460,730,472,580,800 meters

This is roughly equal to:

* 5,878,625,373,184 miles

* 63,241 astronomical units (AU)

In essence, a light-year represents the vast distances involved in astronomy. It's used to describe the immense distances between stars and galaxies.